1. Field of the Invention
The invention relates to a camera which is useful for both close-up and normal range photography in flash and ambient exposure modes, and which has automatic exposure control apparatus for adjusting an exposure aperture in accordance with scene light intensity. More particularly, the invention provides for restricting the exposure aperture automatically, independently of the exposure mode, when the camera is set for a close-up photograph, to enhance depth of field.
2. Description of the Prior Art
Depth of field depends upon aperture and the distance from a camera's lens to the subject. The smaller the aperture the greater the depth of field. However, the closer the subject the smaller the depth of field.
As the camera gets closer to the subject, the depth of field shrinks. The effect can be compensated for--up to a point--by stopping down the lens.
There are known in the prior art cameras which set an exposure aperture automatically as a function of the intensity of ambient light. When the ambient light is low the camera is set at its largest aperture, which provides the maximum amount of exposure light. Because depth of field is small with a relatively large aperture, a camera having exposure control apparatus of this type has a disadvantage when used for close-up photographs in low ambient light if critical subject definition is required.
There are also known in the prior art cameras having a follow-focus flash system. In general, this includes movable diaphragm blades for defining an adjustable exposure aperture as a function of subject distance. The blades are coupled to a flash sensing member and a lens focusing system. For a close-up flash exposure, the exposure aperture is set at its minimum size. A camera having a follow-focus system provides enhanced depth of field for close-up exposures only when a flash is used, which normally occurs in low ambient light.
There is also known in the prior art a camera which coordinates focus setting and aperture size without requiring a flash. U.S. Pat. No. 4,154,517 describes a camera having a manually adjustable diaphragm for regulating an exposure aperture and a focus adjustment device, which can be set at a predetermined position falling outside a normal focus adjusting range. A coordinating device secures an appropriate depth of field by limiting the size of the exposure aperture when the focus adjustment device is set at its predetermined position.